Ersipu ("Two-Four Notation")

Ersipu (literally "two-four notation") is a type of
pitched notation exclusive to
xian shi yue. Apparently primarily designed for the
zheng zither, although also used by the other string instruments
of the ensemble, it makes use of the Chinese characters for numbers
two to eight to indicate the position of individual strings of
the instrument, which is tuned to a pentatonic scale . Its exact
period of origin is uncertain due to lack of documentation.
But it is believed to date back to the middle Tang dynasty period
and to be related to the notation for the 13-stringed zither
that was transplanted to Japan from China during that time, and
which later developed into the
koto zither. The symbols in this Tang dynasty zither
notation mostly consisted of Chinese number characters.

Ersipu is normally written and read from top to bottom,
from right to left. Rhythmic durations of individual notes are
not given, but symbols on the right of the characters indicate
where it falls in the measure (i.e. where on an empty, strong
or weak beat) and note grouping. Besides pitch and meter, ersipu also
expresses extended concepts of mode through
the use of the terms qing (``light``) and zhong (``heavy``) in
connection with the strings of the
zheng zither corresponding to san (6) and liu (3), and the
term huo (``alive``) in connection with the string corresponding
to wu (2). These terms do not appear on the notation itself
but, rather, after the title of the melody, indicating the mode
in which the melody is to be played. The names of the four most
common modes used in xian shi yue are derived from the use of these
terms which
describe the action to be executed on the three mentioned strings.